Preparation of calcium carbide



,M'ch 13, 1956 w. VAN LooN ETAL 2,738,256

PREPARATION oF CALCIUM CARBIDE Filed Dec. ze, 1953 l United States PatentO PREPAnArroN or CALCIUM CARBIDE Willem Van Loon, Geleen, and Sieds ,KoopaL Sittard, Netherlands, assignors vto Stamicarbon N; V., Heerlen, Netherlands Application December 2s, 1953, serial No. 400,769

claims priority, application Netherlands December 30, 1952 z Claims. (Cl. zas-20s) The invention relates to the preparation of calcium carbide in a shaft furnace by the process (hereinafter termed the process as referred to) in which a mixture of a fuel mainly consisting of carbon, such as coke, charcoal or anthracite, and a calcareous compound to be converted into carbide such as unslaked lime, limestone or dolomite is fed into the shaft furnace at the top thereof, and the amount of heat and the temperature needed for the reaction between the carbon and the compound to be converted is produced by burning part of the fuel present by means of an oxygen-containing blast which is injected into the furnace through laterally positioned tuyeres. The product formed collects in the lower part of the shaft furnace in the so-called melt pot, from which it can be discharged through a tap hole, either continuously or periodically.

The invention relates in particular to the manner in which the oxygen-containing blast is fed into the shaft furnace.

Provision should be made for injecting the oxygen-con taining blast so that, on leaving the tuyeres, the blast is distributed as uniformly as possible over the entire horizontal cross sectional area of the furnace in order to obtain a horizontal combustion zone of white-hot fuel.

In the case of blast furnaces this is effected by providing a ring of tuyeres which as a rule are placed in a horizontal position and through which the blast is supplied at a high rate (about 180 m./sec.). The draught in the furnace causes the blast to ascend as a result of which the combustion zone does not extend, or only extends but a short distance, downwardly from the tuyeres, and the fuel in front of the tuyeres is set in strongly turbulent motion.

It has now been found, quite unexpectedly, that in the preparation of calcium carbide, in a shaft furnace the process may be made to proceed more smoothly if the strongly turbulent motion f the fuel in front of the burners can be avoided or reduced. In particular the trouble that the charge of the furnace gets stuck or that even the entire furnace gets blocked if the fuel in the combustion zone is not set in strongly turbulent motion. The step of considerably lowering the injection velocity below the value which is customary as in the blast furnace production of iron, is not in itself sufficient however, since although this step avoids the turbulent motion referred to, the use of a low injection rate causes the formation of a peripheral tire instead of the desired horizontal combustion zone over the entire cross sectional area of the furnace.

Objects charge getting stuck in the shaft furnace is avoided or strongly reduced.

It is another object of this invention to prepare calcium l a shaft furnace is shown.

2,738,256 Patented Mar.1.3vv 195g;

ICC

2 carbide in a shaft furnace in which furnace the fuel in front of the tuyeres is not set in strongly turbulent motion.

A further object of this invention is in the preparation of CaCz in a shaft furnace to inject the oxygen-containing blast so that on leaving the tuyeres the blast is distributed as uniformly as` possible over the entire horizontal cross sectional area of the furnace.

Another object is to obtain in the furnace a horizontal elongated combustion zone of white-hot quietly moving fuel.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter.

General description These objects are accomplished according to the present invention by sloping the tuyeres downwardly towards their free ends.

This slope should not be so great, however, that the oxygen-containing blast comes into contact with the melt as this may lead to rapid oxidation of the molten product with deleterious effects upon the process as a result. It it found that a slope greater than 30 should be avoided.

Accordingly the present invention provides a process as referred to for the preparation of a carbide in a shaft furnace, in which the oxygen-containing blast is supplied at a velocity lower than m./sec. and higher than 40 m./sec. through annularly arranged tuyeres the axes of which slope downwardly towards the free ends of the tuyeres at an angle of 10 to 30 to the horizontal.

lt is preferred to keep the air blast velocity in the range of 50 to 80 m./ sec. Velocities lower than 40 m./sec. are not suitable since in this case the oxygen does not penetrate far enough in a horizontal direction and a peripheral tire may form. If the angle between the tuyeres and the horizontal is greater than 30, it is found that the permissible blast velocities are so low that a good result is not obtained. A reduction of the angle between the tuyere axes and the horizontal plane, below 10, increases the danger of a peripheral fire unless the velocity of the blast is kept so high that a strong turbulence of the fuel in front of the tuyeres is set up which leads to segregation of the charge and the symptom of getting stuck of the charge.

The invention is illustrated by the accompanying drawing wherein a partial vertical section of the lower end of The shaft furnace 1 is provided with a cooling spiral or coil 11 at the level of the combustion zone. Projecting into the furnace are a number of burners 12 through which the oxygen-containing blast is blown into the furnace via a ring conduit 15. The bottom of the shaft furnace is formed by the melting pot 20 from which the product formed is withdrawn through the tap hole 18.

According to the invention the angle between the axes of the burners and the horizontal amounts to 10-30.

Conclusion The present invention provides to a process for the manufacture of calcium carbide in a shaft furnace by starting from a mixture of solid fuel, mainly consisting of carbon, and a calcareous addition in which process part of the fuel present is converted to gases by an oxygen-containing blast in order to provide the amount of heat and the high temperature required for the formation of calcium carbide, which molten carbide is collected in the lower section of the furnace and which can be discharged either continuously or periodically; the process according to the invention being characterized by the fact that the oxygen-containing blast is supplied at a velocity lower than 100 m./sec. and higher than 40 mJsec. through annularly arranged tuyeres the axes of which ing in accordance with the present invention it is possible to prepare calcium carbide in ya shaft furnace in ka very s'rnoth v'v'ay`v`sitlio`utl tlie trouble" th`at the charge I in" the fu'rlilice gets stck'ortht the furnace gets' blocked.

vVCQCYl'-l t t v t 1. In ajp'roces's'foripreparing'cralciiiinc'rbide'in'a' shaft fu'ricefroin a'mixt'ure o'f' a solid fuel comprisiiig'crbon, n'cl a"clca'reo`us` material and'inyol'v'ing thestep'soffa) converting part of said `fuelv to" ges'wth 'an oxygenc'otlinirig blast injected an'n'ula'rly `into said furnace `to p'ride the" heat and temper'tle req'uir'd for c'rbide `ftn'mation, (b) permitting the yresulting gas to escabe through the'tpof the furnacefvyl'iilefA (c) "collecting molten cbiden the lower section of tli`e`fuia`Cei, the improve` ments which comprise injecting the oxygen-containing blast into said furnace atavelocity of between 440 Itru/sec. and 100 IIL/sec. and at an angle of between 10 and 30 to the horizontal.

2. Process according to claim 1, wherein the injection velocity is higher than SOYand'loWer than 80 m./sec.

References Citediin the le of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR PREPARING CALCIUM CARBIDE IN A SHAFT FURNACE FROM A MIXTURE OF A SOLID FUEL COMPRISING CARBON, AND A CALCAREOUS MATERIAL AND INVOLVING THE STEPS OF (A) CONVERTING PART OF SAID FUEL OT GASES WITH AN OXYGENCONTAINING BLAST INJECTED ANNULARLY INTO SAID FURNANCE TO PROVIDE THE HEAT AND TEMPERATURE REQUIRED FOR CARBIDE FORMATION, (B) PERMITTING THE RESULTING GAS TO ESCAPE THROUGH THE TOP OF THE FURNACE WHILE (C) COLLECTING MOLTEN CARBIDE IN THE LOWER SECTION OF THE FURNACE, THE IMPROVEMENTS WHICH COMPRISES INJECTING THE OXYGEN-CONTAINING BLAST INTO SAID FURNACE AT A VELCOITY OF BETWEEN 40 M./SEC. AND 100 M./SEC. AND AT AN ANGLE OF BETWEEN 10* AND 30* TO THE HORIZONTAL. 